Conventional theory of modern drug design challenged

LONDON - New evidence that challenges the current theory about a process key to the way modern drugs are designed and how they work in the human body has been uncovered by the scientists from The Scripps Research Institute.

Currently, the theory about ligands - compounds that bind to proteins and trigger a specific biological action - and how they bind to proteins runs along the lines of a one person-one vote paradigm. Ligands are considered to be the relatively static partner in the process, and easily rejected if the protein dramatically changes shape.

In contrast, working with the molecular systems that recognize the hormone estrogen, the new Scripps Research study found that as protein receptors change shape ligands can adapt to that change, binding productively to both active and inactive structures.

In the current study, the scientists worked with a receptor (which binds substances triggering certain biological effects) for the hormone estrogen and a well-known estrogen receptor antagonist (which blocks the receptor).

Estrogen receptors are activated by the hormone estrogen, which is one of two primary female sex hormones (the other is progesterone). Disturbances in estrogen levels play a role in number of disorders including cancers, heart disease, and stroke in women.

When ligands bind to a specific subset of receptors, the ligands stabilize specific protein conformations, turning on (or off) molecular switches that control diverse cellular functions. For example, the binding of the breast cancer treatment tamoxifen is specific for the inactive conformation of the estrogen receptor - this locks the receptor in place, blocks the active conformation and prevents tumor growth.

“As the protein and ligand move together, each can have a unique affinity, and activity profile, which working together defines the signaling output,” the Nature quoted Kendall Nettles, an associate professor in the Department of Cancer Biology at Scripps Florida, as saying.

The new study was published October 10, 2010 in an advance, online edition of the journal Nature Chemical Biology. (ANI)